1. Field
Example embodiments relate to a nitrogen-containing heteroaromatic ligand-transition metal complex, a buffer layer comprising the complex, an organic thin film transistor and an electronic device comprising the buffer layer and methods of manufacturing the same. Other example embodiments relate to a heteroaromatic ligand-transition metal complex containing nitrogen, a buffer layer comprising the complex, which may improve the injection and transport of electrical charges, an organic thin film transistor and an electronic device comprising the buffer layer and methods of manufacturing the same.
2. Description of the Related Art
Organic material-based device technologies may complement the field of silicon-based electronic devices in the field of large area flexible displays. Organic Thin Film Transistor (OTFT) technologies, which are being researched, may be sufficiently competitive by not requiring integration and providing improved performance, compared to silicon-based Thin Film Transistors (TFTs).
The infrastructure cost of OTFTs may be only about ⅓ of that of amorphous silicon TFTs, and OTFTs may be more easily operated than an inorganic substrate and may be continuously processed. Therefore, the cost of processing OTFTs may be reduced compared to conventional TFTs. In order to apply the OTFTs to the backplane of a display, the characteristics of OTFTs may be improved through the design and synthesis of organic semiconductors, the design of devices and the development of process technologies.
The characteristics of TFTs may be determined by the injection and transport of electrons and holes. Electrons and holes may be injected into a channel layer without causing contact resistance between electrodes and a semiconductor layer, and then the electrons and holes may be more rapidly transported from the channel layer. Unlike silicon TFTs, in which ohmic contact more easily occurs, the characteristics of OTFTs may be mainly deteriorated by contact resistance. When metals come into contact with a semiconductor layer or an electrical charge transfer layer having a relatively low concentration of impurities, a potential barrier may be formed at the contact surface therebetween, thereby increasing resistance. The height of the potential barrier may depend on the difference between energy levels of electrodes and a semiconductor layer or an electrical charge transfer layer, and the state of the connection therebetween.
Conventional methods of surface-treating electrodes, which are used to reduce contact resistance between electrodes and a semiconductor layer or an electrical charge transfer layer, may include methods of using a Self-Assembled Monolayer (SAM) and/or methods of using a buffer layer. Among the methods, the method of using a buffer layer may dispose a layer containing a material for reducing contact resistance between electrodes and a semiconductor layer or an electrical charge transfer layer, and may be mainly applied to a process of producing an organic thin film transistor (OTFT) and/or an organic light emitting diode (OELD).
Low-molecular-weight semiconductors, which may form a film in a vacuum process, e.g., triphenyl amine derivatives and/or acid-doped conductive polymers, which may form a film in a solution process, e.g., poly(3,4-ethylenedioxythiophene) and/or poly(styrenesulfonate), have been used as the buffer layer materials.
Buffer layer materials, which may form a film in a solution process, may be required in order to reduce costs. However, when acid-doped conductive polymers are used as the buffer layer materials, an acid dopant may be diffused to a channel layer, thereby decreasing the stability of devices.